Stored bodies of water, for example swimming pools, unless cared for in accordance with strict regiments, act as breeding grounds for various types of algae which grow in the water and on the sides and bottom of the water body. Algae known as green algae and yellow or mustard algae are particularly troublesome in swimming pools.
Green algae are typically waterborne algae. Once established in pool water green algae are difficult to eradicate other than by shocking the pool with massive doses of chlorine. In most instances this practice is effective on green algae, but takes an inordinate length of time, e.g., 72 hours to clear the water.
Yellow algae grows principally on the walls of the pool and appears as a yellow-brown stain. Yellow algae are not removed by shocking the pool, and once a pool becomes infested the most effective and usual way to eliminate yellow algae is to drain the pool and manually scrub the algae from the wall surfaces. This is time consuming and expensive.
Many agents have been proposed and used for the treatment of stored water bodies such as ponds, lakes, reservoirs, storage tanks, cooling systems, spray ponds, swimming pools, and the like. However, many of these agents are harmful or undesirable to humans. Others, when added, while effectively acting as bacteriostatic, algaestatic, and slime-control agents, have not functioned to decolorize and/or eliminate green and yellow algae once they have become established.
U.S. Pat. No. 4,614,595 discloses a method for clarifying bodies of water and removing staining from the containers thereof, particularly swimming pools, by the addition of a source of ammonium ion and a source of chlorine ion and/or bromine ion. More particularly, the patent discloses a method of treating swimming pools to decolorize algae and to remove undesired stains caused thereby by establishing in the pool water a concentration of chloramines or bromamines sufficient to decolorize the algae by adding to the pool water between about 2 and about 10 ppm ammonium ions and between about 2.75 and about 24.44 ppm chlorine and/or bromine ions, the level of addition of these ions to the pool water being selected to cause the free available chlorine and/or bromine content of the pool water to be substantially depleted. Decolorization typically occurs within a matter of hours and is completed within 24 hours, after which the water is preferably standardized.